1. Field of the Invention
The present invention relates to a wet treatment apparatus for feeding a treatment liquid onto a workpiece to be treated at a wet treatment step, such as a cleaning step, an etching step, and the like, in a process for manufacturing, for example, a semiconductor device, a liquid crystal panel, and the like.
2. Description of the Related Art
In the field of electronic devices, such as semiconductor devices, liquid crystal display panels, and the like, a step for cleaning a semiconductor substrate and a glass substrate (acting as the workpiece to be treated) is indispensable in the manufacturing process thereof. During the cleaning step, the substrate is cleaned with ultrapure water, electrolyte, ozone water, hydrogen gas dissolved water, and the like to remove various substances therefrom in the manufacturing process. These cleaning liquids are typically fed onto the substrate from the nozzle of a cleaning apparatus. However, when a conventional cleaning nozzle is used, an excess amount of cleaning liquid is often used. For example, when trying to achieve a degree of cleanness of about 0.5 piece/cm2 of particles remaining on a substrate of 500 mm square by cleaning the substrate with a cleaning liquid such as electrolyte or the like, and then rinsing it with a rinsing liquid, the cleaning liquid and the rinsing liquid must each be conventionally used in an amount of 25 to 30 L/min.
In an attempt to overcome the above problem, there has been developed a liquid saving type cleaning wet treatment nozzle capable of reducing the amount of cleaning liquid to be used as compared with conventional types of cleaning nozzles. This wet treatment nozzle is used when a substrate to be treated is subjected to wet treatment by feeding a treatment liquid onto the substrate. The wet treatment nozzle includes a treatment liquid introduction path formed at an end, an introduction port for introducing a treatment liquid, a treatment liquid discharge path formed at an end, and a discharge port for discharging the treatment liquid after it is used. An introduction opening and a discharge opening are formed at the other ends of the introduction path and the discharge path, respectively, and open toward the substrate to be treated.
The wet treatment nozzle device as described above also includes a suck and discharge unit for sucking and discharging the treatment liquid that has been in contact with the substrate to be treated after treatment through the discharge path by controlling the pressure difference between the pressure of the treatment liquid in contact with the substrate to be treated and the atmospheric pressure so as to prevent the treatment liquid from flowing to the outside of the discharge path.
The wet treatment apparatus having the above wet treatment nozzle may also have a nozzle or substrate having moving unit for treating the entire region of the surface of the substrate to be treated by relatively moving the wet treatment nozzle along the surface to be treated.
That is, according to the wet treatment apparatus as described above, a liquid saving type nozzle can be utilized that can remove a treatment liquid from the substrate to be treated without causing the treatment liquid to come into contact with any portion other than the portion to which the treatment liquid is directed. Further, the provision of a moving unit for relatively moving the wet treatment nozzle and the substrate to be treated along the surface to be treated of the substrate permits the entire region of the substrate to be subjected to the treatment.
As described above, there have been developed wet treatment apparatuses capable of cleaning the entire surface of a substrate to be treated while reducing the quantity of treatment liquid used. However, the condition under which these wet treatment apparatuses are actually used have not been examined sufficiently.
That is, while it is true that wet treatment apparatuses have been developed as liquid saving type wet treatment apparatuses, the conditions under which they are actually used, such as the flow rate of a treatment liquid for optimizing treatment, an optimum relative moving speed between the substrate to be treated and the wet treatment nozzle, and so on, have only been approximated through trial and error. Thus, not only is a long time needed to determine the conditions under which the wet treatment apparatuses are optimally used, but it is likely that the wet treatment apparatuses are not used under optimum conditions.
An object of the present invention, which was made to solve the above problems, is to identify the appropriate conditions under which a liquid saving type wet treatment apparatus as described above is used, and to provide a wet treatment apparatus capable of being used under optimum conditions, to thereby realize effective and efficient wet treatment.
To solve the above problems, the flow rate was first examined. An optimum flow rate is determined from the condition wherein the treatment liquid uniformly flows from an introduction opening surface to a recovery opening surface, and wherein the wet treatment process can be sufficiently executed with the flow rate. Then, it was necessary to examine an optimum flow rate per unit length in a direction perpendicular to the relatively moving direction of a wet treatment nozzle and a workpiece to be treated, and the value of the optimum flow rate was determined by experimentation.
That is, a wet treatment apparatus according to the present invention includes a nozzle having an approximately rectangular introduction opening surface, which is open toward a workpiece to be treated, and an approximately rectangular recovery opening surface, which is also open toward the workpiece to be treated. The introduction opening surface and the recovery opening surface are flush with each other and are disposed with the long side directions thereof in parallel with each other. The present invention also includes a treatment liquid introduction unit having an introduction flow path for introducing a treatment liquid between the introduction opening surface and the surface to be treated, a treatment liquid recovery unit having a suction pump and a recovery flow path for sucking and recovering the treatment liquid from between the recovery opening surface and the surface to be treated, and a moving unit for relatively moving the nozzle and the workpiece to be treated along the surface to be treated as well as in the short side directions of the introduction opening surface and the recovery opening surface. Wherein the flow rate of the treatment liquid flowing from the introduction opening surface to the recovery opening surface through the surface to be treated of the workpiece to be treated is controlled to 0.02 to 0.3 L/min per 1 cm in the long side direction of the introduction opening surface.
That is, when the flow rate is less than 0.02 L/min, the treatment liquid cannot be sufficiently distributed to the surface to be treated of the workpiece, and also cannot be sufficiently replaced. In contrast, when the flow rate is greater than 0.3 L/min, an excessive treatment liquid flows to the outside of the surface to be treated, and the stable flow of the treatment liquid on the surface to be treated is disturbed, whereby the treatment liquid is likewise insufficiently replaced.
According to the present invention, the treatment liquid is sufficiently distributed to the surface to be treated of the workpiece and is sufficiently replaced. In addition, an excessive treatment liquid does not flow to the outside of the surface to be treated. Therefore, the wet treatment of the workpiece can be effectively executed.
Further, since the wet treatment can be executed with a small amount of treatment liquid, the size of piping, valves, an apparatus for manufacturing and delivering the treatment liquid, such as pure water, etc., can be reduced, and the size of a wet treatment apparatus can likewise be reduced, thereby decreasing treatment costs.
In the present invention, the flow rate can be controlled by regulating the sectional area of the introduction flow path and/or the recovery flow path. As a method of controlling the sectional area of each flow path, the present inventions employs a method of disposing a regulator valve in a midway of the piping for forming the flow path, a method of switching a flow path having a large sectional area and a flow path having a small sectional area, or the like. A method of using a fluid mass flow controller and the like can also be appropriately employed as another flow rate control method.
In the present invention, it is preferable that the lengths of the long sides of the introduction opening surface and the recovery opening surface be equal to or larger than the width, which is in the direction parallel to the long sides, of the workpiece to be treated. This allows the entire surface of the workpiece to be treated by relatively moving the nozzle and the workpiece with the moving unit only once in one direction. Therefore, the time for treating the overall workpiece can be reduced.
In the present invention, it is preferable to set a relative moving speed due to the moving unit to 0.5 to 20 cm/sec. When the moving speed is less than 0.5 cm/sec, the time for treating the overall surface to be treated is increased wastefully. Moreover, when bubbles are generated during treatment, they are deposited on the surface to be treated and the surface cannot be sufficiently treated.
In contrast, when the moving speed is greater than 20 cm/sec, a treatment liquid layer on the surface to be treated is broken by a shear force that is generated thereby, and the surface cannot be sufficiently treated during the treatment. In addition, problems such as an increase in vibration of the treatment apparatus and the like are liable to occur.
In the present invention, it is preferable that the distance between the respective opening surfaces and the surface to be treated of the workpiece be 0.5 to 6 mm. When this distance is less than 0.5 mm, a resistance that is necessary for the treatment liquid to move is increased excessively. Moreover, it is difficult to secure the flow rate of 0.02 to 0.3 L/min per 1 cm in the long side direction of the introduction opening surface. Further, contact of the nozzle with the workpiece is liable to be caused by the vibration of the treatment apparatus.
In contrast, when the distance is greater than 6 mm, it is difficult to keep the treatment liquid between the respective opening surfaces and the surface to be treated, and air is liable to flow therebetween. Thus, it is difficult to stably flow the treatment liquid between the nozzle and the workpiece, and as a result, a portion may not be treated.
In the present invention, it is preferable that the short sides of the respective opening surfaces have a length of 0.01 to 2 cm. When the short sides of the respective opening surfaces are less than 0.01 cm, the resistance that is necessary for the treatment liquid to move is increased excessively, and it is difficult to secure a flow rate of 0.02 to 0.3 L/min per 1 cm in the long side direction of the introduction opening surface.
In contrast, when the short sides of the respective opening surfaces are greater than 2 cm, the treatment liquid cannot be uniformly fed from the introduction opening surface to the surface to be treated, and the treatment liquid on the surface to be treated cannot be uniformly recovered from the recovery opening surface, whereby the flow rate of the treatment liquid on the surface to be treated becomes uneven.
In the present invention, an ultrasonic oscillation application unit may be interposed between the introduction opening surface and the recovery opening surface to apply ultrasonic oscillation to the treatment liquid on the workpiece. In this case, ultrasonic oscillation can be applied to the treatment liquid on the surface to be treated, whereby the efficiency of a wet treatment process such as cleaning and the like can be improved.
In the present invention, an oxidation-reduction potential controller and a pH controller may be provided for the treatment liquid. In this case, since the composition and the concentration of the treatment liquid can be optimally maintained, a sufficient treatment efficiency can be secured even if the flow rate has a small value.